The number of students from non-English speaking backgrounds gaining admission to Sydney's top selective high school has fallen significantly in the past two years.

James Ruse Agricultural High School used to have the highest number of students from a language background other than English (LBOTE) of any selective school, making up between 94 and 96 per cent of year 7 enrolments between 2007 and 2010.

But that percentage fell to 83 per cent in 2011 and to 79 per cent last year, according to data released by the NSW Department of Education and Communities.